Dampening device for lithographic presses

ABSTRACT

A dampening system for a printing press which includes a resilient metering roller which is concave in plan profile, having a diameter at its ends which is larger than the diameter over the central portion so as to develop relatively higher contact pressure at its ends for blocking off flow of dampening fluid in the end regions when printing a sheet of small size. Means are provided for skewing the metering roller to selectively reduce the pressure at the ends for securing a more nearly uniform axial distribution for the printing of sheets of full roller width. The skewing may be augmented to compensate for any bowing which may occur in the rollers. The skewing is effected by mounting the metering roller on individually swingable arms with means for differential adjustment of the arms. Eccentrics at the ends of the metering roller enable adjustment of the pressure.

United States Patent v [1 1 Krochert et al.

[ DAMPENING DEVICE FOR LITHOGRAPHIC PRESSES inventors: Karl Heinz Kriichert, Offenbach;

Karl Zimmermann, Darmstadt, both of Germany Roland Offsetmaschineenfabrik Faber & Schleicher AG, Offenbach/Main, Germany Filed: Oct. 19,1971

Appl. No.: 190,491

[73] Assignee:

[30] Foreign Application Priority Data A Nov. 6, 1970 Germany P 20 54 678.5

US. Cl. 101/148, 101/350 I Int. Cl. B4lf 7/26, B4lf 7/40 Field of Search 101/148, 348-352, 101/206, 207, 208

References Cited UNITED STATES PATENTS 10/1919 Linder 101/148 UX 9/1941 Knowlton 118/262 9/1956 Varga et al. 101/148 UX 11 3,744,414 1 July 10, 1973 3,343,484 9/1967 Dahlgren 101/148 3,433,155 3/1969 Norton 101/148 I Primary Examiner-J. Reed Fisher [57] ABSTRACT A dampening system for a printing press which includes a resilient metering roller which is concave in plan profile, havinga diameter at its ends which is larger than the diameter over the central portion so as to develop relatively higher contact pressure at its ends for blocking off flow of dampening fluid in the end regions when printing a sheet of small size. Means are provided for skewing the metering roller to selectively reduce the pressure at the ends for securing a more nearly uniform axial distribution for the printing of sheets of full roller width. The skewing may be augmented to compensate for any bowing which may occur in the rollers. The skewing is effected by mounting the metering roller on individually swingable arms with means for differential adjustment of the arms. Eccentrics at the ends of the metering roller enable adjustment of the pressure.

7 Claims, 6 Drawing Figures PAIENTED JUL 1 men SHEEI 1 OF 2 SOURCE OF wk 36 IN vsu'ran Mez-k/wzWa/ur he: Z/MMEkM/M/V @,%%m4% 1 I'TYS.

PAIENTEU JUL 1 0 I973 sum 2 or 2 SOURCE OF INK INVENTOR 1 ,M MJ, ',wam

0% Arrr .DAMPENING DEVICE FOR LITHOGRAPHIC PRESSES Dampening devices are normally constructed so as to produce even distribution of water or other dampening fluid over the entire width of the applicator roller and plate cylinder. Where sheets of narrower than standard size are to be printed the water fed from the ends of the applicator roller is not consumed and tends to accumulate to produce a flooding condition. Steps have been taken in the past to reduce the flow of dampening fluid at the ends or in other localized regions of the applicator roller but this has required troublesome conversion when the press is again set up for the printing of full size sheets. Steps have also been taken to compensate for axial variations .in feed due to slight bowing of rollers running in pressure engagement.

Accordingly it is an object of the invention to provide a dampening system which is capable of feeding a film of dampening fluid uniformly along the length of an applicator roller for theprinting of full size sheets.

It is a related object to provide a dampening system which may be used universally for narrow sheets as well as sheets of full width, which may be switched from one width condition to the other, which is consistent permitting original operating conditions to be precisely reestablished, and which is inherently inexpensive both for inclusion in new presses and for conversion of presses in the field to incorporate the inventive features. It is yet another object to provide means for controlling the width of a wetted path which serves also to achieve effective bowing compensation.

Other objects and advantages of the invention will become apparent upon reading the attached detailed description and upon reference to the drawings in which:

FIG. 1 is an elevational view of a dampening system incorporating the present invention.

FIG. 2 is a-fragmentary plan view of the system set forth in FIG. 1.

FIG. 3 is an elevational view'of the system shown in FIG. 1 but with the metering roller skewed for feeding of an axially uniform film of fluid.

FIG. 4 is a plan view corresponding to FIG. 3.

FIGS. 5 and 6 are fragmentary elevations showing means for calibrating the skew and pressure adjustments.

While the invention has been described in connection with a preferred embodiment, it will be understood that we do not intend to be limited to the particular embodiment as shown but intend, on the contrary, to cover the various alternative and equivalent constructions included within the spirit and scope of the appended claims.

Turning now to the drawings there is disclosed a portion of a lithographic printing press including a dampening system generally indicated at 10 which cooperates with a plate cylinder 11. As is well known in the operation of a lithographic press it is necessary to apply to the surface of the plate on the plate cylinder a film of ink which adheres to the ink receptive areas and a film of dampening fluid which adheres to the non-ink receptive areas. For applying a film of ink to the plate an ink applicator or form roller 12 is used, fed, for example, through a series of rollers (not shown), from a suitable source of ink 13. For the purpose of transmitting a film of dampening fluid to the plate, a water fountain 20 is provided having a body 21 of water or other dampening fluid and having a fountain roller 22. The fountain roller 1 22 which is preferably hardsurfaced is rotated in the fountain, preferably at a speed lower than press surface speed, by a drive mechanism 23. The fountain roller 22 is rotated in the direction of the arrow to provide an ascending or feed side 24, to which the fluid clings, and a descending or return side 25. Each roller in a series has such feed side and return side. lnterposed between the fountain roller 22 and the plate cylinder is a resiliently surfaced applicator roller 26 which issometimes referred to as a water form roller. If desired, a transfer roller-(not shown) may be interposed between the fountain roller and the applicator roller.

In accordance with the present invention a metering roller is provided running in pressing engagement with the feed side of the fountain roller or other rollers in the fluid system, the metering roller having a concave plan profile with a larger diameter at the ends than over the central portion so as to relatively augment the pressure applied at the ends thereby to block passage of fluid at the ends for printing of sheets of less than full roller width, the metering roller having means for adjustably skewing it with respect to the fountain roller so as to reduce the pressure applied at the ends of the metering roller for achieving substantially uniform axial distribution of fluid for printing of sheets of full roller width and to compensate for any bowing tendency. More specifically the metering roller is journaled in a pair of arms which are independently swingable about the axis of the engaged roller and having independent adjusting means coupled to the press frame for adjusting the degree of skew. Thus, referring to the, drawings, a resilient metering roller 30 is provided having a central portion 31 and end portions 32. Projecting from the metering roller are stub shafts 33, 33a which are journaled in bearings 34, 34a. The bearings are mounted in levers 35, 350 which are mounted for independent swinging movement coaxially with respect to the fountain roller 22.

When the levers 35, 350 are alined, as shown in FIGS. 1 and 2, the metering roller.30 is parallel to the axis of the fountain roller 22 which it engages. To adjust the pressure between the metering roller and fountain roller, eccentrics 36, 36a having adjusting arms 37, 37a are interposed between the levers and the bearings of the metering roller.

The metering roller is so formed as to be concave in plan profile, having a diameter d] over its central portion and a diameter d2 at the ends. As a result, when the eccentrics 36, 36a are symmetrically adjusted so that the metering roller applies pressure to the fountain roller, the pressureat the ends of the metering roller is augmented by reason of the larger diameter and is greater than that'which exists over the central portion of the metering roller. The high pressure at the ends of the metering roller effectively blocks passage of a film of dampening fluid in the end positions so that a film of fluid is transmitted (as indicated by the stipp ling) only over the central portionof the fountain roller, via the central portion of the applicator roller, to the central portion of the plate cylinder for printing of sheets having a width N less than the width of the rollers. This prevents the flooding at the endsof the dampening rollers which is usually encountered in presses where the film is fed more or less uniformly over the entire axial width of the rollers in the dampener system.

In carrying out the invention means are provided for differentially adjusting the swingable levers 35, 35a so that the metering roller is skewed relative to the axis of the fountain roller which it engages, such skewing serving to move the ends of the metering roller relatively away from the axis of the fountain roller thereby to reduce the pressure exerted by the ends of the metering roller and permitting a more uniform flow of dampening fluid over the entire length of the metering roller for printing of sheets of full roller width. To accomplish this a linkage including a threaded element is interposed between each of the levers 35, a and the press frame. Taking the lever 35 by way of example, a link is pinned to the lever at one end 41. At its opposite end 42 the link is pinned to a non-rotatable screw 43. The screw is threaded into a nut 44 which is rotatable by a knob 45 but which is captive, in the endwise direction, in the press frame indicated at 46. Corresponding elements, with subscript a, are provided for adjusting the remaining lever 35a.

With the arms differentially adjusted as shown in FIGS. 3 and 4, the metering roller 30 is skewed into the position shown thus reducing the pressure applied by the ends of the metering roller upon the fountain roller. The degree of skew may be so adjusted that the pressure applied by the metering roller is uniform along the entire length of the metering roller so that a film of dampening fluid of constant thickness, indicated by the stippling, is fed to a wide printing area indicated at W for printing of sheets of wide, i.e., standard, width.

' It will be seen then that when switching the press from printing of narrow sheets to printing of sheets of standard width it is a simple matter to adjust the control knobs 45, 450 from a symmetrical condition, in which the metering roller is parallel to the other rollers in the system, to a differential condition in which the metering roller is skewed. For convenience in making the adjustment, and for enabling a given adjustment to be reproduced when returning to a particular mode of operation, the skew control knobs may be calibrated as shown in FIG. 5, the calibration being such as to account for turning of the knob through a number of revolutions. As shown in this figure the knob 45 is provided with a pinion which engages a gear 51 having a pointer 52 which cooperates with a scale 53. To establish the condition shown in FIGS. 1 and 2, both of the pointers may be set to the zero reference position. To achieve skew, one or both of the control knobs may be rotated to predetermined scale positions. If desired, the eccentrics 36, 36a may be calibrated, as shown in FIG. 6. A scale 55 may be secured to the lever 35 and cooperating directly with the eccentric adjusting arm 37.

While the invention has been described in connection with a metering roller which cooperates directly with the fountain roller, it will be apparent that the present invention is not limited thereto but contemplates use of a metering roller of concave profile mounted for skewing adjustment with respect to the feed side of any roller in the fluid feeding system. For example the metering roller may be mounted for pressing engagement with the applicator roller 26, with the ends swingable, for skewing purposes, about the axis of the applicator roller. Alternatively, the metering roller may be mounted in pressing engagement with any transfer roller which may be interposed between the fountain roller 22 and applicator roller 26. Accordingly, as used herein, the term roller means is intended to be sufficiently broad as to include any roller within a dampening system which consists of a number of rollers interposed in the path of fluid transfer.

While the invention has been described above in connection with rollers which are sufficiently stiff as to substantially resist bowing, it is one of the further features of the present invention that use of a metering roller of concave profile with provision for skew may be utilized without change or addition to compensate for the effects of bowing. As is well known, bowing occurring in any one ofa series of rollers by reason of the total pressure load between them results in a nonuniform distribution of the unit pressure. Thus the middle of the roller which is supported less stiffly than the ends tends to have a lower per unit pressure at the region of engagement. As a result there is a tendency to feed a thicker film of fluid at the center of a bowed roller than at the ends. This center feeding tendency may be readily overcome in the present construction by skewing the metering roller to an angle beyond that which would apply if the rollers were perfectly stiff and unbowing. Using the present invention, axial uniformity of fluid or standard width, even where relatively thin and flexible rollers are used, simply by turning the skew knob, or knobs, an augmented amount to provide even less per unit pressure, relatively speaking, at the ends of the metering roller and with the desired total pressure being restored, if desired, by touch-up adjustment at the eccentrics. The skew setting and eccentric adjustment corresponding to the condition of uniform feeding of fluid for the printing of a sheet of full width may be noted and the settings reestablished at any future time upon the calibration scales without any special tailoring adjustment and by a press operator who is relatively unskilled but capable of resetting the adjustment on the scales as a purely routine or mechanical procedure.

In the preferred embodiment of the invention the me tering roller is made of resilient material, for example, synthetic rubber running in engagement with a hard surfaced roller, for example, the fountain roller in the fluid feed system. If desired, and without departing from the invention, the metering roller may be of hard surfaced construction cooperating with the feeding side of a resilient roller in the fluid feed system. A hard surfaced metering roller could, for example, engage the undersurface of the form roller 26. If this were done, the arms 35,35a and the associated adjusting means could be retained, with the arms swiveling about the stubshafts of the form roller rather than about the stubshafts of the fountain roller.

Also while the invention is particularly applicable to the supplying of dampening fluid, it will be apparent that the invention in its broader aspect is not limited to use with dampening fluid but is applicable wherever there is need for adjusting the axial distribution of a film of fluid fed between a set of cooperating rollers. For example, the invention may be employed in the feeding of ink in an ink supply system entirely analogously to the feeding of water or the like in a dampening system and where it is desired to ink only the central section of a printing cylinder for the printing of sheets of narrow width or for the purpose of compensating for the bowing of the ink-feeding cylinders. Thus, the term dampening fluid as used herein is not to be limited to water or the like but may be construed to cover any fluid which is to be fed in the form of a film to a printing plate or other cylindrical receiving surface.

What we claim is:

1. In a dampening system for lithograph press having a frame journaling a plate cylinder, the combination comprising a source of dampening fluid, roller means including a plurality of serially arranged rollers coupled to the source for forming and transferring a film ofdampening fluid to the plate cylinder, a metering roller running in pressing engagement with the feeding side of one of the serially arranged rollers for determining the thickness of the film, at least the metering roller or the roller which it engages being resiliently surfaced, the metering roller being concave in plan profile having a larger diameter at its ends than over its central portion so as to relatively augment the pressure applied by the metering roller at its ends thereby to block transfer of dampening fluid at the ends of the roller means when the metering roller and roller means are substantially parallel for printing of sheets of narrow width, means for mounting the metering roller for adjustable skewing movement thereby to enable adjustment of the metering roller to a skewed position relative to the roller means in which the ends of the metering roller are moved relatively away from the roller which it engages to achieve substantially uniform axial distribution of the pressure exerted by the metering roller for printing of sheets of substantially full roller width.

2. The combination as claimed in claim 1 in which the metering roller is formed of resilient material and the roller which it engages is hard surfaced.

3. The combination as claimed in claim 1 in which the rollers exert a substantial degree of pressure upon one another and in which the mounting means for the metering roller has a range of adjusting movement for skew to produce a degree of skew beyond the amount theoretically required for even distributionof the fluid thereby to compensate for non-uniform distribution of pressure between the rollers resulting from the tendency of the rollers to flex or bow by reason of their pressure engagement with one another.

4. In a dampening system for lithograph press having a frame journaling a plate cylinder, the combination comprising a fountain roller rotatably driven in a fountain having a supply of dampening fluid, an applicator roller interposed between the fountain roller and the plate cylinder for conveying a film of dampening fluid to the plate cylinder, a resilient metering roller running in pressing engagement with the feeding site of the fountain roller for determining the thickness of the film on the fountain roller which is available for transfer to the applicator roller, the metering roller having a concave plan profile with a larger diameter at the ends than over the central portion so as to relatively augment the pressure applied by the metering roller at its ends thereby to block passage of fluid at the ends when the metering roller is substantially parallel to the fountain roller while providing a substantially even axial distribution of fluid over the central portion of the applica tor roller for the printing of sheets of less than the full roller width, and means for adjustably skewing the metering roller with respect to the fountain, roller to reduce the pressure applied at the ends of the metering roller for achieving substantially uniform distribution of fluid along the axis of the applicator roller for the printing of sheets of full roller width.

5. In a dampening system for lithograph press having a frame journaling a plate cylinder, the combination comprising a source of dampening fluid, roller means comprising a plurality of serially arranged rollers coupled to the source for forming a film of dampening fluid and including an application roller for applying the fluid to the plate cylinder, a metering roller running in engagement with the feeding side of one of the serially arranged rollers for determining the thickness of the film, at least the metering roller or the roller which it engages being resiliently surfaced, the metering roller fluid at the ends of the roller means when the metering roller and roller means are substantially parallel for printing of sheets of narrow width, the metering roller being journaled in a pair of independently swingable.

levers coaxial with the engaged roller and having means for differentially adjusting the angular positions of the levers thereby to enable swinging of the metering roller to a skewed position relative to the engaged roller for more uniform axial distribution of the pressure exerted by the metering roller to-equalize flow of dampening fluid along the axis of the applicator roller when printing sheets of substantially full roller width.

6. In the combination as claimed in claim 5, the levers each having journals for engaging the ends of the metering roller and eccentrics interposed between the levers and the respective journals for varying the pressure applied by the metering roller against the engaged roller.

7. The combination as claimed in claim 5 in which linkages including respective threaded elements are interposed between the press frame and the levers for individual adjustment of the angular positions of the levers. 

1. In a dampening system for lithograph press having a frame journaling a plate cylinder, the combinaTion comprising a source of dampening fluid, roller means including a plurality of serially arranged rollers coupled to the source for forming and transferring a film of dampening fluid to the plate cylinder, a metering roller running in pressing engagement with the feeding side of one of the serially arranged rollers for determining the thickness of the film, at least the metering roller or the roller which it engages being resiliently surfaced, the metering roller being concave in plan profile having a larger diameter at its ends than over its central portion so as to relatively augment the pressure applied by the metering roller at its ends thereby to block transfer of dampening fluid at the ends of the roller means when the metering roller and roller means are substantially parallel for printing of sheets of narrow width, means for mounting the metering roller for adjustable skewing movement thereby to enable adjustment of the metering roller to a skewed position relative to the roller means in which the ends of the metering roller are moved relatively away from the roller which it engages to achieve substantially uniform axial distribution of the pressure exerted by the metering roller for printing of sheets of substantially full roller width.
 2. The combination as claimed in claim 1 in which the metering roller is formed of resilient material and the roller which it engages is hard surfaced.
 3. The combination as claimed in claim 1 in which the rollers exert a substantial degree of pressure upon one another and in which the mounting means for the metering roller has a range of adjusting movement for skew to produce a degree of skew beyond the amount theoretically required for even distribution of the fluid thereby to compensate for non-uniform distribution of pressure between the rollers resulting from the tendency of the rollers to flex or bow by reason of their pressure engagement with one another.
 4. In a dampening system for lithograph press having a frame journaling a plate cylinder, the combination comprising a fountain roller rotatably driven in a fountain having a supply of dampening fluid, an applicator roller interposed between the fountain roller and the plate cylinder for conveying a film of dampening fluid to the plate cylinder, a resilient metering roller running in pressing engagement with the feeding site of the fountain roller for determining the thickness of the film on the fountain roller which is available for transfer to the applicator roller, the metering roller having a concave plan profile with a larger diameter at the ends than over the central portion so as to relatively augment the pressure applied by the metering roller at its ends thereby to block passage of fluid at the ends when the metering roller is substantially parallel to the fountain roller while providing a substantially even axial distribution of fluid over the central portion of the applicator roller for the printing of sheets of less than the full roller width, and means for adjustably skewing the metering roller with respect to the fountain roller to reduce the pressure applied at the ends of the metering roller for achieving substantially uniform distribution of fluid along the axis of the applicator roller for the printing of sheets of full roller width.
 5. In a dampening system for lithograph press having a frame journaling a plate cylinder, the combination comprising a source of dampening fluid, roller means comprising a plurality of serially arranged rollers coupled to the source for forming a film of dampening fluid and including an application roller for applying the fluid to the plate cylinder, a metering roller running in engagement with the feeding side of one of the serially arranged rollers for determining the thickness of the film, at least the metering roller or the roller which it engages being resiliently surfaced, the metering roller being concave in plan profile having a larger diameter at its ends than over its central portion so as to relatively Augment the pressure applied by the metering roller at its ends thereby to block transfer of dampening fluid at the ends of the roller means when the metering roller and roller means are substantially parallel for printing of sheets of narrow width, the metering roller being journaled in a pair of independently swingable levers coaxial with the engaged roller and having means for differentially adjusting the angular positions of the levers thereby to enable swinging of the metering roller to a skewed position relative to the engaged roller for more uniform axial distribution of the pressure exerted by the metering roller to equalize flow of dampening fluid along the axis of the applicator roller when printing sheets of substantially full roller width.
 6. In the combination as claimed in claim 5, the levers each having journals for engaging the ends of the metering roller and eccentrics interposed between the levers and the respective journals for varying the pressure applied by the metering roller against the engaged roller.
 7. The combination as claimed in claim 5 in which linkages including respective threaded elements are interposed between the press frame and the levers for individual adjustment of the angular positions of the levers. 